1. Field of the Invention
The present invention relates to a thin film transistor liquid crystal display device in which a connection method between an indium tin oxide layer and an aluminum layer on a substrate is improved and a fabricating process therefor.
2. Related Art
Aluminum as interconnect material has an advantage of a low resistivity and, in recent years, has widely been used in interconnection or an electrode, such as gate interconnection and source interconnection on a substrate, in a thin film transistor liquid crystal display device. When indium tin oxide (hereinafter referred to as ITO) which is used for a transparent pixel electrode of a thin film transistor liquid crystal display device or the like directly contacts with aluminum, however, oxygen in ITO is extracted by aluminum and as a result, a resistance of a contact section is increased.
Therefore, in a conventional thin film transistor liquid crystal display device, there has been adopted the structure of no contact between an aluminum layer and an ITO layer. For example, as shown in FIG. 3, a conductive barrier layer 33 made of tungsten or the like is provided in advance so as to cover an aluminum layer 32 formed on a substrate and a contact hole 35 which reaches the barrier layer 33 is formed in an insulating layer 34 so that the barrier layer 33 and the ITO layer 36 contact with each other, whereby the aluminum layer 32 and the ITO layer 36 are mutually brought into a electrical connection with the barrier layer 33 interposed therebetween. Alternately, as shown in FIG. 4, a metal layer 42 made of a metal other than aluminum and an aluminum layer 43 are formed on a substrate and a contact hole 45 which reaches an surface of the metal layer 42 is formed through an insulating layer 44 and the aluminum layer 43 so that the metal layer 42 and an ITO layer 46 are brought into contact with each other in the contact hole 45, whereby the aluminum layer 43 and the ITO layer 46 are electrically connected to each other with the metal layer 42 made of a metal other than aluminum interposed therebetween.
In the contact structure shown in FIG. 3, since an interconnect pattern is formed by two layers comprising the aluminum layer 32 and the barrier layer 33, there is a necessity for forming the insulating layer 34 after etching of the two layers. When the interconnect pattern is produced by the etching, however, different etchants are respectively applied to the aluminum and barrier layers, which requires two etching operations respectively using different etchants to make a process complicated. Besides, in the contact structure shown in FIG. 4, it is required that after the metal layer 42 made of a metal other than aluminum, the aluminum layer 43 and the insulating layer 44 are formed, the insulating layer 44 and the aluminum layer 43 are respectively etched to expose a surface of the metal layer 42, which is a problem because of increase in the number of process steps.